The invention relates to cooling systems for downhole tools.
A wellbore is typically a hostile environment, with downhole temperatures capable of reaching well over 500xc2x0 F. Such elevated temperatures can damage heat-sensitive components of tools lowered into the wellbore to perform various activities, such as logging, perforating, and so forth. Examples of such heat-sensitive components include explosives and detonating cords used in a perforating apparatus or batteries and electronic circuitry in other devices.
Conventionally, to avoid damage to heat-sensitive components in tools lowered into wellbores having elevated temperatures, the tools must be quickly inserted and retrieved from the well to perform the desired activities. Generally, this is practical only in vertical wells. In highly deviated or horizontal wells, in which insertion and retrieval of tools are relatively slow processes, the length of time in which the tools are kept in the wellbores at elevated temperatures could cause damage to heat-sensitive equipment.
In some logging tools, dewar flasks have been used to protect heat-sensitive equipment. A dewar flask is generally tubular and contains a vacuum layer that reduces heat transfer. Heat-sensitive components are placed in the inner bore of the dewar flask. By using the dewar flask, the rate of temperature rise is reduced to allow the logging tools to stay downhole longer. However, a need continues to exist for more effective techniques of reducing the rate of temperature rise of components lowered into a wellbore.
In general, in one embodiment, an apparatus for cooling a component inside a tool includes a heat sink positioned next to the component. An insulation layer surrounds the component to reduce heat transfer to the component.
Other features and embodiments will become apparent from the following description and from the claims.